The Euphorbiaceae family is rich in plants with a long history of human medicinal applications [Watt, J. M. and M. G. Breyer-Brandwijk, "The Medicinal and Poisonous Plants of Sourthern and Eastern Africa," 2nd Ed., E. S. Livingstone Ltd., London, 1962, p. 426] [Morton, J. F., "Major Medicinal Plants," C. C. Thomas, Springfield, Ill., 1977, pp. 193, 366]. The Euphorbiaceae genus Phyllanthus contains about 600 species ranging from free floating aquatic forms to trees, including several species that have been employed in the primitive treatment of cancer [Hartwell, J. L., Lloydia, 32, 157 (1969)] [Spjut, R. W. and R. E. Perdue, Cancer Treatment Reports, 60, 979 (1976)]. Because of the U.S. National Cancer Institute's (NCI) exploratory plant evaluation program, in collaboration with the U.S. Department of Agriculture (USDA), the roots of a tree believed at the time to be P. brasiliensis Muell were collected about a decade ago in Costa Rica. An ethanol extract of the original collection was found to inhibit growth of the NCI murine P388 lymphocytic leukemia (PS) system, and the Kupchan group [Kupchan, S. M., E. J. LaVoie, A. R. Brankfman, B. Y. Fei, W. M. Bright and R. F. Bryan, J. Am. Chem. Soc., 99, 3199 (1977)] isolated and partially characterized a PS active glycoside termed phyllanthoside from a 1974 recollection. It is now believed that the roots from which Kupchan et al. isolated phyllanthoside came from P. acuminatus Vahl rather than P. brasiliensis.